Effect of calcitonin on experimental osteolathyrism. (II). Action of calcitonin on collagen metabolism.

In order to study the effect of calcitonin on the bone collagen metabolism in osteolathyrism, male Wistar rats were placed on 0.1% aminoacetonitrile diet for 9 days. Porcine calcitonin dissolved in gelatin was concurrently administered in a dose of 0.1 MRC U/100g body weight for 8 days and on the 9th day 0.75 MRC U/100g body weight was given 3, 2 and 1hr respectively before sacrifice. Both bone collagen formation and maturation were examined by the determination of specific and total activities of 3Hhydroxyproline in bone collagen, and collagen resorption was examined by the estimation of the amount of hydroxyproline released into the incubation medium from metaphyses. Treatment of lathyritic rats with calcitonin diminished the concentration of serum calcium, phosphate, and rate of collagen resorption, but did not affect collagen formation and collagen maturation. Inhibitory effect of calcitonin on collagen resorption was more pronounced in osteolathyrism than under normal condition. It seemed that parathyroid glands did not play a vital role in the collagen resorption induced by osteolathyrism, since the resorption was not affected by parathyroidectomy. On the other hand, administration of calcitonin (every 0.8 MRC U/rat, 60 and 30min before sacrifice) also counteracted collagen resorption which was induced by low calcium diet and treatment with parathyroid hormone (PTH, 70 USP units). It is concluded that the effect of calcitonin on collagen metabolism resulted in primary inhibition of collagen resorption in osteolathyrism, and that calcitonin counteracted both PTH-dependent collagen resorption and PTH-independent collagen resorption induced by osteolathyrism.